1. Saute the onion in the oil in a large pot over medium-low heat until softened, about 3 minutes. Add the chicken broth, tomatoes, clam juice, basil, salt, fennel seeds, black pepper, red-pepper flakes and the 1 cup water. Bring to boiling. Lower the heat; cover and simmer for about 15 minutes.
2. Meanwhile, melt butter in small skillet. Stir in flour until smooth. Cook over low heat, stirring often, until flour is browned, for about 5 minutes. Cool slightly.
3. Stir about 1 cup of the soup into flour mixture until smooth. Stir into soup in pot. Bring to boiling, stirring constantly. Add fish, lemon juice and olives. Cook gently, uncovered, for 5 to 10 minutes or until fish is cooked through. Garnish with parsley if you wish. Makes 4 servings.